Nah, doing this would also break things like carousels/slideshows too, as well as menus that slide in from off screen.

And while it's rarer than those, I've definitely also seen page components which show a preview of the content until you click on them, then expand to show everything else. Those would break as well.

So while you'd certainly block modal popups that prevent scrolling, you'd also break a bunch of things on other sites that use the overflow property for more legitimate reasons.